/* @flow */

const { escape } = require('he')

import { SSR_ATTR } from 'shared/constants'
import { RenderContext } from './render-context'
import { compileToFunctions } from 'web/compiler/index'
import { createComponentInstanceForVnode } from 'core/vdom/create-component'

import { isDef, isUndef, isTrue } from 'shared/util'

let warned = Object.create(null)
const warnOnce = msg => {
  if (!warned[msg]) {
    warned[msg] = true
    console.warn(`\n\u001b[31m${msg}\u001b[39m\n`)
  }
}

/*从来存放模板template与template的编译结果的缓存器，避免重复编译*/
const compilationCache = Object.create(null)
/*将template模板编译成render函数*/
const normalizeRender = vm => {
  const { render, template } = vm.$options
  if (isUndef(render)) {
    if (template) {
      const renderFns = (
        compilationCache[template] ||
        (compilationCache[template] = compileToFunctions(template))
      )
      Object.assign(vm.$options, renderFns)
    } else {
      throw new Error(
        `render function or template not defined in component: ${
          vm.$options.name || vm.$options._componentTag || 'anonymous'
        }`
      )
    }
  }
}

function renderNode (node, isRoot, context) {
  if (isDef(node.componentOptions)) {
    renderComponent(node, isRoot, context)
  } else {
    if (isDef(node.tag)) {
      renderElement(node, isRoot, context)
    } else if (isTrue(node.isComment)) {
      context.write(
        `<!--${node.text}-->`,
        context.next
      )
    } else {
      context.write(
        node.raw ? node.text : escape(String(node.text)),
        context.next
      )
    }
  }
}

function renderComponent (node, isRoot, context) {
  const { write, next, userContext } = context

  // check cache hit
  const Ctor = node.componentOptions.Ctor
  const getKey = Ctor.options.serverCacheKey
  const name = Ctor.options.name

  // exposed by vue-loader, need to call this if cache hit because
  // component lifecycle hooks will not be called.
  const registerComponent = Ctor.options._ssrRegister
  if (write.caching && isDef(registerComponent)) {
    write.componentBuffer[write.componentBuffer.length - 1].add(registerComponent)
  }

  const cache = context.cache
  if (isDef(getKey) && isDef(cache) && isDef(name)) {
    const key = name + '::' + getKey(node.componentOptions.propsData)
    const { has, get } = context
    if (isDef(has)) {
      has(key, hit => {
        if (hit === true && isDef(get)) {
          get(key, res => {
            if (isDef(registerComponent)) {
              registerComponent(userContext)
            }
            res.components.forEach(register => register(userContext))
            write(res.html, next)
          })
        } else {
          renderComponentWithCache(node, isRoot, key, context)
        }
      })
    } else if (isDef(get)) {
      get(key, res => {
        if (isDef(res)) {
          if (isDef(registerComponent)) {
            registerComponent(userContext)
          }
          res.components.forEach(register => register(userContext))
          write(res.html, next)
        } else {
          renderComponentWithCache(node, isRoot, key, context)
        }
      })
    }
  } else {
    if (isDef(getKey) && isUndef(cache)) {
      warnOnce(
        `[vue-server-renderer] Component ${
          Ctor.options.name || '(anonymous)'
        } implemented serverCacheKey, ` +
        'but no cache was provided to the renderer.'
      )
    }
    if (isDef(getKey) && isUndef(name)) {
      warnOnce(
        `[vue-server-renderer] Components that implement "serverCacheKey" ` +
        `must also define a unique "name" option.`
      )
    }
    renderComponentInner(node, isRoot, context)
  }
}

function renderComponentWithCache (node, isRoot, key, context) {
  const write = context.write
  write.caching = true
  const buffer = write.cacheBuffer
  const bufferIndex = buffer.push('') - 1
  const componentBuffer = write.componentBuffer
  componentBuffer.push(new Set())
  context.renderStates.push({
    type: 'ComponentWithCache',
    key,
    buffer,
    bufferIndex,
    componentBuffer
  })
  renderComponentInner(node, isRoot, context)
}

function renderComponentInner (node, isRoot, context) {
  const prevActive = context.activeInstance
  // expose userContext on vnode
  node.ssrContext = context.userContext
  const child = context.activeInstance = createComponentInstanceForVnode(
    node,
    context.activeInstance
  )
  node.ssrContext = null
  normalizeRender(child)
  const childNode = child._render()
  childNode.parent = node
  context.renderStates.push({
    type: 'Component',
    prevActive
  })
  renderNode(childNode, isRoot, context)
}

function renderElement (el, isRoot, context) {
  if (isTrue(isRoot)) {
    if (!el.data) el.data = {}
    if (!el.data.attrs) el.data.attrs = {}
    el.data.attrs[SSR_ATTR] = 'true'
  }
  const startTag = renderStartingTag(el, context)
  const endTag = `</${el.tag}>`
  const { write, next } = context
  if (context.isUnaryTag(el.tag)) {
    write(startTag, next)
  } else if (isUndef(el.children) || el.children.length === 0) {
    write(startTag + endTag, next)
  } else {
    const children: Array<VNode> = el.children
    context.renderStates.push({
      type: 'Element',
      rendered: 0,
      total: children.length,
      endTag, children
    })
    write(startTag, next)
  }
}

function hasAncestorData (node: VNode) {
  const parentNode = node.parent
  return isDef(parentNode) && (isDef(parentNode.data) || hasAncestorData(parentNode))
}

function getVShowDirectiveInfo (node: VNode): ?VNodeDirective {
  let dir: VNodeDirective
  let tmp

  while (isDef(node)) {
    if (node.data && node.data.directives) {
      tmp = node.data.directives.find(dir => dir.name === 'show')
      if (tmp) {
        dir = tmp
      }
    }
    node = node.parent
  }
  return dir
}

function renderStartingTag (node: VNode, context) {
  let markup = `<${node.tag}`
  const { directives, modules } = context

  // construct synthetic data for module processing
  // because modules like style also produce code by parent VNode data
  if (isUndef(node.data) && hasAncestorData(node)) {
    node.data = {}
  }
  if (isDef(node.data)) {
    // check directives
    const dirs = node.data.directives
    if (dirs) {
      for (let i = 0; i < dirs.length; i++) {
        const name = dirs[i].name
        const dirRenderer = directives[name]
        if (dirRenderer && name !== 'show') {
          // directives mutate the node's data
          // which then gets rendered by modules
          dirRenderer(node, dirs[i])
        }
      }
    }

    // v-show directive needs to be merged from parent to child
    const vshowDirectiveInfo = getVShowDirectiveInfo(node)
    if (vshowDirectiveInfo) {
      directives.show(node, vshowDirectiveInfo)
    }

    // apply other modules
    for (let i = 0; i < modules.length; i++) {
      const res = modules[i](node)
      if (res) {
        markup += res
      }
    }
  }
  // attach scoped CSS ID
  let scopeId
  const activeInstance = context.activeInstance
  if (isDef(activeInstance) &&
      activeInstance !== node.context &&
      isDef(scopeId = activeInstance.$options._scopeId)) {
    markup += ` ${(scopeId: any)}`
  }
  while (isDef(node)) {
    if (isDef(scopeId = node.context.$options._scopeId)) {
      markup += ` ${scopeId}`
    }
    node = node.parent
  }
  return markup + '>'
}

/*创建render函数*/
export function createRenderFunction (
  modules: Array<Function>,
  directives: Object,
  isUnaryTag: Function,
  cache: any
) {
  return function render (
    component: Component,
    write: (text: string, next: Function) => void,
    userContext: ?Object,
    done: Function
  ) {
    warned = Object.create(null)
    const context = new RenderContext({
      activeInstance: component,
      userContext,
      write, done, renderNode,
      isUnaryTag, modules, directives,
      cache
    })
    /*将template模板编译成render函数*/
    normalizeRender(component)
    renderNode(component._render(), true, context)
  }
}
